“Kerosene Welding “ Damascus by John White, Master Smith

A couple of folks have asked me to do a write-up on“Kerosene Welding” Damascus. Here ‘tis.

Let me say that Ron Newton and J.W.Randal first egged me onto try this method. Thanks, guys! Also, a 2010 discussion on “Kerosene vs Flux”on this forum set me on a course of study to a better understanding of thenature of welding with kerosene.

* Why Kerosene?

The first question to be asked is, “Why kerosene rather thanflux?” The answer is that kerosene welding is just one more step in the searchfor perfect, cleanly welded Damascus, with absolutely no bad welds, noinclusions; Damascus which shows your chosen pattern in transparent clarity. Withno flux in the initial weld, there is no possibility of even the tiniest flux inclusion in the final blade. Kerosene welding is something to add to yourrepertoire of methods that make for clean welded steel.

A side benefit of switching to kerosene welding is themuch-reduced use of flux in your forge, the lessoned need to rebuild the floorfrom the flux build-up, and less “flux-splatter” during welding. We’ll stilluse a bit of flux at one stage, but much less than before.

*How does it work?

The second question usually asked is “How does it work?” Theanswer is the “oxidation-reduction reaction.” Anytime we “burn” something,carbon, for example, we are “ oxidizing” it by combining the carbon with oxygen,to form carbon monoxide or carbon dioxide. At the same time, we are “reducing”something of the oxygen needed for the combination. If we burn wood in open air, we oxidize the (carbon in the) wood, and reduce the (oxygen in the) air.

When we put a billet soaked in kerosene into a forge,running at welding temperature, and with the “reducing atmosphere” we know weneed, the volatiles will quickly vaporize and burn off outside the forge in alarge swirl of flame. The billet will be left covered with a thin film ofcarbon that you can actually see as a black dusting. The “reducing “atmosphereof the forge did not provide enough oxygen to completely burn up the carbon inthe kerosene.

As the billet continues to heat, however, the very active carbon looks for oxygen to combine with. If there’s not enough oxygen in the forge atmosphere, that oxygen can be found in any scale, rust, or other oxidation on the steel. The carbon left on the billet oxidizes into carbon monoxide and carbon dioxide and escapes theforge. The scale or rust, which is some variation of an Iron Oxide, is reducedof its’ oxygen, leaving pure iron behind.

Here’s a quote from Steve Culver from a 2010 discussion onthe American Bladesmith forum that describes the process ,

“ When the kerosene soaked billet is placed into the fire, thelighter volatile elements quickly burn off, leaving behind carbon. The carbonwith its higher ignition point remains between the layers of steel until thesteel heats to the temperature where combustion of the carbon can begin. Theproper reducing forge fire, being oxygen deficient, forces the carbon to seekoxygen from a source other than the atmosphere of the fire to sustaincombustion. The carbon finds the oxygen it requires in the forge scale (i.e.,iron oxide; FeO) on the steel. By pulling the oxygen from the iron oxide, thecarbon effectively changes the iron oxide back into iron (Fe).”

Kerosene welding works then, by cleaning the steel, in analready reducing atmosphere. By the way, folks have noted that it’s notnecessary to grind off the mill scale from your 1084 when welding withkerosene. That’s true, but the carbon left on the billet combines with theoxygen in the scale in a strict chemical ratio. It’s being used up, as itworks. I give it a head start by using clean steel.

*Reducing Atmosphere

Let’s start at the first, then. It is necessary that you be welding in a strongly reducing atmosphere. If your atmosphere is oxidizing oreven neutral, you’re going to have all sorts of problems. I’m going to assume,also, that you’re welding out of a vertical type, blown propane or natural gasforge. It’s true that people can weld in anything from charcoal, to coal or coke, and in horizontal atmospheric forges with hot spots. I’m going to consistently recommend methods and materials that minimize un-controlled variables and make things simpler and easier.

When your forge is running at a welding heat, and properlyadjusted, you should have an orange flame burning 4-5 inches out the opening.This indicates a reducing atmosphere inside the forge. That is, you areintroducing too much gas into the forge to burn up with the amount of airyou’re putting in. There is no excess oxygen inside the forge body, and the gasis exiting the opening to burn outside.

Check it by increasing gas flow slightly. The flame should extend. If you reduce gas flow,the flame will shorten, and finally disappear into the forge. You now have anoxidizing atmosphere, which would create scale on your billet. Bring the flameback out by increasing gas flow. The orange “dragon’s breath” you’ve heardabout is your visual and audible indicator of a reducing atmosphere.

*Temperature Control

Next, let’s move to temperature control. Many of us learnedto judge welding temps by the color of the billet, and how the flux “dances” on the steel. We all know of the Master who’s been doing this for thirty years, and can do it all “by eye.” Simply putting a thermocouple in the forge, andreading exact temperatures can shorten that thirty-year apprenticeship considerably, and eliminate one more uncontrolled variable from your methods.

The KMQXL 125 G6 thermocouple from Omega.com is a 6 inch by1/8^th inch Inconel-clad thermocouple which can be inserted throughthe side of the forge, even with the opening, by simply drilling a 1/8^thinch hole through the side of the forge. There is no need of a well, and thisthermocouple , designed to operate in a gas flame, will last until you beat it to death with a billet. Bring the tip of the thermocouple even with the edge of the front and back openings, so it will read the temps an inch or so from your billet.

*Welding Temperature

When I’m welding, I run the forge at 2315 degrees F. Even a few degrees hotter seems not to allow enough “recovery” time between heats to get the billet back up to welding temp without “soaking.” Cooler? Well, it’ll weld at cooler temps, for sure, but we’re back to controlled variables. Afterputting a cold billet into the forge, the temp will knock down to somewhere around 2150 or so, depending on the size of the billet. Over about 12-14minutes the temp will climb, and as it rolls through 2300 exactly, I’ll pull it out and weld. The welding temperature is one less thing to guess at.

*Cutting and Stacking

If you’re trying for perfection in your welded billets,you’ve surely moved on already from hot cutting to cold cutting, grindingclean, and re-stacking. It’s for sure you don’t want to stick a hot billet intoa container of kerosene. That’s how they make fuel-air bombs. To save time, I’ll usually be welding threeor four billets at a time. By the time the last billet is welded, I can turn off the forge, and begin to cut, grind clean, and re-stack the first. I can get through three or four weld cycles,on three or four billets, in a working day. So, we’ll be planning on the cold cut, grind, and re-stack method when we kerosene weld.

*Anhydrous Borax

As a last suggestion for reducing mess and problems, let mesuggest you use anhydrous borax for that little bit of flux we’re going to useat one stage of this process. I get mine from Kelly Cupples. It doesn’t costmuch, and you’re only going to use a little bit. It doesn’t ball up and fall off the billet like regular Borax, and this not only makes for a cleaner forge,but for quicker work, and no need to remove the billet from the forge andre-flux.

*The Kerosene Welding Pass

OK, let’s work through a welding pass using the kerosenemethod. Tack your billet together and weld to a handle in the usual manner. Youare using a MIG with Argon/CO2, or TIG-ing the billet together, aren’t you?We’re trying for absolute cleanliness here.

Have some sort of metal container of K-1 kerosene sitting in a safe place. Place the billet in the kerosene, and leave it in there long enough to soak between all the layers. Place the wet billet in the forge,running a reducing atmosphere, at your welding heat. The volatiles will burn off quickly, leaving a layer of soot. Do not remove the billet from the forge until ready to weld.

The billet will come up to heat in the usual way, and show the colors you’re used to. When welding temperature is reached, (2300 degreesfor me, read out on my digital read-out,) remove the billet and make your first welding passes.

You’ll be pleased to find no flux splatter or smoke from theweld. I always take my first weld long-ways on my power hammer dies, flip it over for a second pass, thereby welding the center of the billet, then immediately pull two passes cross-ways on the dies, securely welding the edges.

*The Second (Fluxed) Pass

After this first set of passes, the weld is set “green,” andyou’ll want to re-heat and make a second set of welding passes before you drawthe billet out. Here’s where you’ll use a bit of anhydrous flux.

When you brought thehot billet out into the air to weld it, the oxygen in the shop air began toattack the surface of the billet. You’ll find the welds to be cleaner than fluxwelds, but the surface and edges seem to be burned more than with flux. If you simply stick the billet back into the forge, bring it back up to temp, weld and draw out, you’ll find you have to grind off more scale from the surface and edges than you would with a flux weld.

The solution is to quickly wire brush the billet after the first set of welding passes, flux it lightly with anhydrous borax, and place it back in the forge to come up to heat for a second set of welding passes. Since you’ve set the welds cleanly the first time, no flux can get between the layers, and the second welding set with flux will clean up the edges and surfaces.

After the billet is drawn out, set it aside to cool, andmove on to your other billets. With planning, you won’t be losing that much more time compared to hot cutting, and all these things together can move you a step or two further along the path toward more perfect Damascus. That is, until the next problem occurs…

Thank you for sharing your techniques with us John!